The present invention relates generally to underground bore location systems.
Those of ordinary skill in the art should recognize that the term xe2x80x9chorizontal borexe2x80x9d refers to the excavation of a hole, typically for utilities, through the ground and to the excavated hole itself. The present invention relates to systems and methods for locating such bores, but also to such systems and methods for locating existing buried utilities, whether such existing utilities were initially installed by boring or trenching techniques. Accordingly, unless otherwise indicated, the term xe2x80x9cborexe2x80x9d as used herein refers to new bores and to existing buried utilities or similar lines.
Boring location systems are utilized in a variety of circumstances. For example, in horizontal boring systems as are typically used for installing utilities, it is desirable to maintain a directional boring head in a desired boring path and to avoid known obstacles such as existing utilities. Accordingly, systems are known to trace existing utilities from an above-ground position.
The boring head, which may include a boring probe behind a drill head, is underground and is therefore not visible to the operator. Accordingly, the boring probe may be configured to transmit signals from the bore that provide location information to an above-ground operator. One system that is configured to determine whether an underground boring probe is laterally offset from its intended horizontal path is described in U.S. Pat. No. 4,881,083, the entire disclosure of which is incorporated herein by reference. This information is used, in turn, to maintain the boring head in its desired path. Typically, however, an above-ground receiver must be disposed at a known location relative to the boring head with respect to the head""s desired path of travel in order to properly read certain location information. For example, assume that a boring head is to the right of its desired path and that an above-ground receiver is disposed along the path in an attempt to receive location information from which to determine whether the boring head should turn to the right or to the left to regain or maintain its path. Using one conventional receiver, the operator must know whether the boring head is ahead of or behind the above-ground receiver with respect to the desired path.
The present invention recognizes and addresses disadvantages of prior art constructions and methods. Accordingly, it is an object of the present invention to provide an improved bore location system.
This and other objects are achieved by a system for locating a horizontal bore below a ground surface. The system includes a transmitting source configured to radiate from the bore a dipole magnetic field aligned with the bore. A receiver includes a first coil and a second coil, the axis of each coil being orthogonal to the axis of each other coil. A measurement device in communication with the coils is configured to measure the phase of signals induced in the coils by the magnetic field when the axis of the first coil is horizontally perpendicular to the axis of the magnetic field and the axis of the second coil is vertically perpendicular to the axis of the magnetic field and to determine the lateral position of the transmitting source relative to the coils responsively to the phase of the signals induced on the two coils.
A method according to the present invention for locating a horizontal bore below a ground surface includes providing a transmitting source in the bore and radiating from the bore a dipole magnetic field aligned with the bore. A receiver having first and second orthogonally aligned receiver coils is disposed remotely from the bore so that the dipole magnetic field induces a signal in each coil. A measurement device determines the phase of the induced signal of each coil when the axis of the first coil is horizontally perpendicular to the magnetic field axis and the axis of the second coil is vertically perpendicular to the magnetic field axis. The measurement device determines the lateral position of the transmitting source relative to the coils responsively to the phases of the first and second coils.